Fluid heater with guided convection elements



Aug 7, 1956 D. T. cous-HUN 2,757,649

FLUID HEATERv WITH GUIDED CONI/'ECTION ELEMENTS vFiled Sept. 9, '1952 2Sheets-Sheet l INVENTOR.

ATTORNEY ug- 7, 19:56 D. T. couGHLlN 2,757,649

i v FLUID HEATER WITH GUIDED CONVECTION ELEMENTS Filed sept. 9, 1952- v2 sheets-sheet 2 I I I INVENTOR.

BY Q44 ATTORNEY United States Patent Oflice 2,757,649 Patented Aug. 7,195.6

FLUID HEATER WITH GUIDED CONVECTION ELEMENTS Daniel T. Coughlin,Wadsworth, Ohio, assigner to The Babcock & Wilcox Company, New York, N.Y., a corporation ot New Jersey Application September 9, 1952, SerialNo. 308,651 '1'1 Claims. (Cl. 122-478) This invention relates toimprovements in a vapor generating and vapor heating unit employing apendent type convection vapor heater.

When vapor generating and vapor heating units of the pertinent type areoperated. at high gas temperatures, it has been found that certainconstituents of the gases have corrosive effects upon the pertinentmetal, which is greatly increased as metal temperature increases.

Certain-sulphur compounds and vanadium compounds resultingy from thecombustion of oil fuel attack the metals of` the vapor generating andvapor heating units, and it is known that the rate of attack of some ofthese compounds increases with a rise in metal temperature. This isparticularly true when the temperature equals or exceeds the approximatemelting point of 1290 F. (of the compound). This thermal acceleration ofthe rate of corrosion attack, at least occurs in the burning of oilfuels which include. a vanadium compound and the accelerated attack maybe due to a combination of the action of sulphur and vanadium compounds,with the latter acting as a catalyzer.-

This corrosive veffect has been particularly recognized as of importancein the construction and maintenance of the intersection guides whichfunction to maintain the operative relationship of the components ofconvection vapor heating means of the pendent type. The sections of suchvapor heating means are readily pendently supported from structureswhich are not affected by the furnace gases, but, in many installations,the lower ends of the vapor heater sections are disposed at positionswholly exposed to the furnace gases and the sections must be free tomove downwardly under the inuenee of the thermal changes to which theyare subjected. The lower ends of the sections are guided in their spacedrelationship, and if it were attempted to accomplish this result bytheuse of intersection guides disposed below the sections, and, therefore,in line with the maximum expansion movements of the sections, it wouldbe found that the metal of the guides would have such extensive exposureto the furnace gases that the guides would be subject to excessivelyhigh temperatures, and hence subject to substantial destructive effectsby the corrosive constituents of the furnacegases.

This invention provides a construction whereby the guides are maintainedat such low temperatures (1250" F. or below) that such destructive orcorrosive effects are minimized. The pertinent guides also have aminimum of surface exposed to the gases.

The invention involves 'pendent vapor heater sections disposedtransversely of a gas pass with the vapor generating tubes of the floorof the Ygas pass having parts closely associated with the lower ends ofthe vapor heater sections. Specifically, these parts involve steppedportions, or steps. Each step of the floor tubes involves an inclinedportion and an upright portion disposed in proximity of the downstreamside of a vapor heater section. The section is maintained inoperativeposition by an intersection guide having interengaging and slidablyrelated parts, one of which is secured'to a vapor generating iloor tubeand the other to the adjacent rearmost tube of the adjacent vapor heatersection, thus promoting adequate heat transfer from the guide to itsattached floor tube by decreasing the ratio of the gas exposed area ofthe guide to its cross section, and decreasing the ratio of that area tothe length of the guide, while permitting the vapor heater section tohave adequate upright movements relative to the vapor generating tubesunder the influencesof different temperature changes. The lower ends ofthe pertinent vapor heater sections are disposed at a level below thelevel of the associated guides, the guides being associated with theupright parts of the steps of the pertinent generating tubes.

In the pertinent unit the oor of the vapor heating gas pass is supportedfrom the saturated temperature side wall tubes, and the tubular elementsof the, vapor heating means, reach a temperature much higher than thatof the said wall tubes, which are top hung. Thus, there is relativemovement between the lower ends of the vapor heating tube sections andthe inclined oor on which the intersection guides are mounted. Forexample, if we consider a 30 ft. high vapor heating element constructedof an alloy steel known as 18-8 and reaching a metal temperature of1100o F., as compared to the saturated temperature of 600 F., adiiferential movement of the order of 2.4 takes place. At the lower endsof the vapor heating sections, the pertinent arrangement of elementsinvolved in this invention permits such relative movement whileydisposing the outer or high temperature end of each intersection guideat such proximity to the oor tube to which it is welded that heat isconducted to the tube fast enough to keep the metal temperature of theguide within the desired limits.

The specific combination covered by the invention is set forth in theclaims, but for a better understanding 0f the invention and itscharacteristics, references should be had to the accompanyingdescription and drawings which dis. close a preferred embodiment of theinvention.

In the drawings:

Fig. l is a sectional side elevation of a vapor generating and vaporheating unit involving the invention;

Fig. 2 is a partial sectional side elevation showing, on an enlargedscale, the illustrative arrangement of the vapor heater sections, thestepped vapor generating tubes, and the associated intersection guides,in sectional side elevation;

Fig. 3 is a detailed view showing the arrangement of the upright partsof a step of a vapor generating tube in its relation to an associatedvapor heater platen and the co-acting intersection guide; and

Fig. 4 is a horizontal section on the line 4 4 of Fig` 3.

The vapor generating and vapor heating unit shown in the drawingincludes vapor heating means in the form of three banks or groups Vofupright tubes or tube sections indicated at lil, l2, and talas extendingacross the ilow of heating gases from the furnace lo. ln the particularunit shown in the drawings, the bank of tubes 10 constitutes a part of avapor superheater and the banks of Vtubes i2 and lf3 constitute a Vaporreheater, but for the purposes of disclosure of this invention, thesesuccessive banks of tubes might also be successive parts of the samevapor superheater, or unitary vapor heating means. The pertinent banksof tubes are connected to pendently supported headers 13, 20, 22, and24. ln turn, these headers are pendently supported from the steelwork 26by pendent supports generally indicated at 951-98. The banks of tubes10, 12, and 14 of the vapor heater means are disposed transversely of agasl wall 34, and the upper parts of these tubes continue as a screen 40across the gas exit of the vapor heating gas pass, then continue alongthe roof of the gas pass to the vapor and liquid drum 38, which is topsupported by hangers such as 37. The roof sections are pendentlysupported by arrangements of elements such as the fixed beam 39 and thependent support 41. At the iioor of the gas pass the vapor generatingtubes are supported from fixed transverse beams such as 45, 45', and 49xed at their ends to the side wall vapor generating tubes of the unit(not shown).

While the floor of the superheater gas pass is supported on the top hungside wall vapor generating tubes and moves downwardly to some degreewith a temperature increase, the superheater elements expand downwardlyto a greater extent when the unit is brought up to operating pressure.This is due to the fact that the superheater clernents are heated to ahigher temperature and may also be due to the different metallicconstituency of the superheater elements.

The shorter vapor heating tubes 14 are associated with the steps 32 ofthe pertinent vapor generating tubes and the longer reheat vapor heatingtubes or tube sections are associated with the steps 28, the vaporheating tube sections (or bank of tubes) 12 of the intermediate f lengthbeing similarly associated with the steps 30. The steps have uprightparts 42-44 (Fig. 2) disposed in proximity to the rearmost tubes of thecorresponding vapor heating sections 10, 12, and 14. They are shown innear parallelism therewith so that the sections may be etlectivelymaintained in their operative relationships by the associatedintersection guides at 46-48. Each guide (Fig. 4) consists of a metallicT-member 50 with its base welded to the associated upright part 44 of avapor generating tube, the T-head 52 of the part 50 being freelyslidable within a T-slot of the metallic guide member 54 which is weldedto a rearmost tube 14 of a vapor heating section.

With this arrangement, each guide is adequately cooled by reason of itsclose association with a vapor generating tube to which it is secured,and also by reason of its short length and decreased area subject to gascontact.

The lower ends of the sections are disposed at levels below the levelsof the associated guides, but they have such clearance relative to theinclined parts 60-62 of the vapor generating tube steps that adequatevertical movements of the vapor heating sections resulting from theirthermal expansion are permitted.

The vapor generating unit with which the pertinent vapor heating meansis associated further includes groups of burners 62 and 64 disposedalong the front wall 66 of the furnace 16. Fuel and air streams areprojected into the furnace between the vapor generating wall tubes 68which extend from the lower header 70 to the steam and water drum 38.

Beyond the gas outlet of the vapor heating gas pass, there is a gasturning chamber 72 at the top of a downow gas pass 74 having the walls76 and 78. The upper part of this gas pass has superheater inlet tubes80 and 82 disposed along its walls and connected to the inlet header 84of a primary convection superheater 86. The tubes of this superheaterlead to an outlet header 88 which is appropriately connected to theinlet header of the secondary superheater formed by the rows of tubesections 10. The superheater inlet tubes 80 and 82 are supplied withsteam from the steam space of the drum 38 through the tubes 90 and theinterposed header 92. In Fig. 2 the header 92 is shown as pendentlysupported from the steelwork 26 by hangers 94.

The remainder of the illustrative vapor heating means includes thereheater headers 22 and 24 one of which is appropriately connected tothe exhaust of a turbine to supply low pressure and low temperaturevapor to be heated in the banks of tubes 12 and 14. The other reheaterheader is connected to a turbine or turbine stage.

While in accordance with the provisions of the statutes, I haveillustrated and described herein the best form and mode of operation ofthe invention now known to me, those skilled in the art will understandthat changes may be made in the form of the apparatus disclosed withoutdeparting from the spirit of the invention covered by my claims, andthat certain features of my invention may sometimes be used to advantage'ithout a corresponding use of other features.

What is claimed is:

l. in a vapor generating and vapor heating unit, a convection vaporheater having pendently supported upright tubular sections, wall meansforming a gas pass in which the sections are disposed, said wall meansincluding fluid cooled tubes defining a gas pass boundary atjacentcorresponding ends of said sections, corresponding ends oi the sectionsbeing movable relative to said gas pass boundary under temperaturechanges, the uid cooled tubes having small parts bent out of the generaldirection of the tubes and disposed in close proximity to portions ofsaid sections and extending in the general direction of the movement ofthe sections under temperature changes, and guide means includingtransversely extending interengaging components connected to saidsections and said bent out parts of the boundary tubes for maintainingthe convection vapor heater sections in their operative relationshipduring relative vertical movements of said sections and the fluid cooledtubes, said guide means being disposed directly downstream of theadjacent vapor heater sections in the gas ow path.

2. In tiuid heat exchange apparatus, convection vapor heating meansincluding a bank of horizontally spaced upright tubes extendingtransversely of gas ow, means normally providing for a ow of vaporthrough said tubes, means pendently supporting said vapor heating tubes,wall means including a bottom forming a gas pass in which said uprightvapor heating tubes are disposed, said wall means including vaporgenerating tubes disposed in alignment along the bottom of the gas passso as to pass through positions adjacent the lower ends of the vaporheating tubes, the vapor heating tubes being movable relative to thevapor generating tubes at the bottom of the gas pass, the vaporgenerating tubes having small upright portions bent out of the generaldirection of the pertinent tubes and disposed in close proximity tolower portions of the rearmost vapor heating tubes and extending in thegeneral direction of movement of said upright parts of the vapor heatingtubes, and guide constructions each comprising interengaging andrelatively slidably movable parts one of which is secured to a vaporheating tube and the other secured to the adjacent upright part of oneof the vapor generating tubes, said interengaging parts being adapted tohave relative vertical movements.

3. In a vapor generating and vapor heating unit, a convection vaporheater presenting a bank of spaced upright tubes normally extendingtransversely of gas ow, means securing said tubes in groups with eachgroup arranged to form a panel or platen, means connecting the upper andlower ends of the adjacent vapor heating tubes of each platen to providefor series tiow of vapor through the platen, means pendently supportingthe platens, wall means including a bottom forming a gas pass in whichthe platens are disposed, said wall means including vapor generatingtubes arranged in alignment along the bottom of the gas pass,corresponding lower ends of the platens being movable relative to thegas pass bottom under temperature changes, the vapor generating tubes ofsaid bottom having small upright portions closely adjacent uprightportions of selected platen tubes and bent out of the general directionof the vapor generating tubes and extending in the general direction ofmovement of the platen tubes under temperature changes, and giudeconstructions for a plurality of the platens, each guide constructionincluding interengaging parts one of which is fixed to a rearmost platentube and the other txed to the bent out upright part of one of the-vaporgenerating tubes, the interengaging parts of each guide constructionbeing capable of relative vertical movements.

4. In a vapor generating and superheating unit, a furnace havingboundary surfaces defined by rows of vapor generating tubes, wall meansincluding parts of some of said tubes and defining the floor of aconvection vapor heating gas pass leading from the furnace, a bank ofupright convection vapor heating tubes forming rows of pendentlysupported platens with their lower end portions disposed in successivesteps at different Vertical positions, some of said gas pass floor tubeshaving small portions bent out of the general direction of the pertinenttubes, said bent out portions forming successive steps with the uprighttube portions of the steps extending in the general direction ofmovement of the vapor heating tubes under temperature changes, the vaporheating tubes at corresponding ends of the platens being disposed inproximity to said upright parts of the steps, and intersection guidemeans including interengaging relatively slidable parts securedrespectively to said upright portions and the adjacent upright parts ofthe platen tubes to maintain their proximity relationship duringrelative movements of the platens and the floor to the gas pass.

5. In a vapor generating and vapor heating unit, a furnace having vaporgenerating tubes included in its walls, Wall means forming a gas passleading from the furnace, said wall means including parts of same saidvapor generating tubes, some of said vapor generating tubes of the gaspass having multiple bends bent out of the general direction of thetubes and forming successive steps of an inclined wall or floor of thegas pass, a bank of upright convection vapor heating tubes forming rowsof pendently supported platens with the lower ends of the platensarranged in sucessive rows and disposed in successive steps of the vaporgenerating floor tubes, the steps of said floor tubes having uprightparts disposed rearwardly of the inclined parts of the oor tubes, thelower ends of the platens of the vapor heating tubes being movablerelative to said oor under temperature changes and the steps of saidfloor tubes extending in the general direction of movement of theplatens under temperature changes, the vapor heating tubes atcorresponding ends of the platens being disposed in proximity to theupright parts of the steps, and intersection guide means includinginterengaging relatively slidable parts secured respectively to theupright parts of the steps and the rear most tubes of the platens tomaintain the proximity relationship of the upright parts and tubes whilepermitting the platens to move vertically relative to the floor tubes.

6. In a vapor generating and vapor heating unit, a vapor generatingsystem including a furnace with vapor generating tubes in its walls,wall means forming a vapor heater gas pass leading from the furnace,said wall means including a floor with vapor generating tubes thereinhaving multiple bends of parts bent out of the general direction of thetubes and forming a plurality of successive steps, said steps of the oortubes including upright parts, sections of pendent vapor heating tubesdisposed in the gas pass and across the path of gas ow from said furnaceand having the lower parts of successive sections disposed in successivesteps of the oor tubes with the rearmost tubes of said successivesections disposed closely adjacent said upright step parts, the uprightstep parts extending in the general direction of expansion andcontraction movements of the lower parts of the vapor heating tubes, andintersection guide means including interengaging and relatively slidableparts secured respectively to the upright parts of the steps and theadjacent parts of the vapor heating tubes, the relatively slidablemovements of the parts of the guide means taking place in a verticalsense.

7. In a vapor generating and superheating unit, a convection superheaterincluding a bank of spaced upright tubes extending transversely of gasflow, means pendently supporting said superheater tubes, a oor and wallmeans forming ay gas pass in which the superheater tubes are disposed,said means includingvapor generating tubes disposed along the oor of thegas pass and adjacent to the lower ends of the superheater tubes, thelower ends of the superheater tubes being movable relative to the gaspass floor under temperature changes, the vapor generating gas passfloor tubes having small parts bent out of the general direction of thetubes and disposed in close proximity to the rearmost superheater tubesand extending in the general direction of expansion and contractionmovements of the superheater tubes, said bent out parts being uprightand transversely aligned across the gas pass, and intersection guideconstructions each comprising interengaging parts one of which issecured to a rearmost superheater tube and the other secured to one ofthe upright bent out parts ofthe gas pass floor tubes, saidinterengaging parts of the guide constructions being so associated as tohave relative upright slidable movements.

8. In a vapor generating and vapor heating unit, a convection vaporheater presenting a bank of spaced upright tubes extending transverselyof gas liow, means for securing said tubes in groups with each grouparranged to form a flat section or platen, means connecting the upperand lower ends of the adjacent heater tubes of each section to providefor the series tlow of vaporl therethrough, means pendently supportingthe heater sections from a position above a gas pass, vapor generatingtubes arranged in alignment along the floor of the gas pass so as topass through a position adjacent the lower ends of the heater sections,said vapor generating tubes having upright parts disposed closelyadjacent the upright lower portions of the rearmost heater tubes of thesections and extending in the general direction of movement of the vaporheating tubes under temperature changes, and intersection guideconstructions each comprising interengaging parts one of which issecured to a heater tube and the other secured to the upright part ofone of an adjacent vapor generating tube, the interengaging parts ofeach guide construction being capable of relative vertical movements.

9. ln a vapor generating and vapor heating unit, a vapor generatingsystem including furnace wall tubes, wall means including parts of someof said vapor generating tubes defining a convection vapor heater gaspass leading from the furnace, the vapor generating tubes at the bottomof the gas pass having small portions bent out of the general directionof the tubes and forming a plurality of successive rows of alignedsteps, said steps including upright parts, successive rows of sectionsof pendent heater tubes disposed in said gas pass and across the path ofgas flow from said furnace and having the lower parts of successivesections disposed in said successive steps with the end tubes of thesection disposed closely adjacent to said upright parts, the uprightparts of the steps extending in the general direction of the movement ofthe vapor heating tubes under temperature changes, and intersectionguide means including interengaging and relatively vertical slidableparts secured respectively to said upright parts of the steps and theadjacent end tubes of the heater sections, the guide means beingdisposed downstream of the associated heater sections in a gas flowsense.

l0. In a vapor generating and heating unit, a convection vapor heaterpresenting a gas pass and a bank of spaced upright tubes extendingtransversely of the ow of a gaseous heat exchange medium, means normallyproviding for a ow of vapor through said tubes, means pendentlysupporting said heater tubes, vapor generating tubes arranged inalignment along the floor of the gas pass, said vapor generating tubeshaving transversely aligned small upright parts bent out of the generaldirection of the tubes and disposed closely adjacent the rearmost heatertubes, said upright parts extending in the general direction of themovement of the vapor heating tubes under temperature changes, andintersection guide constructions each comprising interengaging parts oneof which is secured to a rearmost heater tube and the other secured tothe upright part of one of the vapor generating oor tubes, saidinterengaging parts of the guide constructions being so constructed andassociated as to have relative upright slidable movements.

l1. A convection uid heater comprising a plurality of heater tubesections each including a seires of connected parallel tube lengths,wall means forming a gas pass in which the sections are disposed, saidwall means including uid cooled tubes dening a gas pass boundaryadjacent corresponding ends of the sections, said corresponding ends ofthe sections being movable relative to said boundary under temperaturechanges, the uid cooled tubes having small parts bent out of the generaldirection of the tubes and disposed in close proximity to the outsidetubes of the heater sections and extending in the general direction ofmovement of the sections 20 under temperature changes, and intersectionguide constructions each including relatively movable interengagingmetallic parts one of which is fixed to an outside heater tube sectionor length and the other fixed to one of the small bent-cnt parts of theuid cooled boundary tubes, said inter-engaging parts of the guideconstructions being capable of relative movements in the generaldirection of expansion of the heater tube sections due to temperatureincreases.

References Cited in the file of this patent UNITED STATES PATENTS1,859,858 Wright May 24, 1932 1,931,639 Armacost Oct. 24, 1933 2,114,224Jacobus Apr. 12, 1938 2,427,031 Toomey et al. Sept. 9, 1947 2,477,950Bailey Aug. 2, 1949 2,536,072 McDonald Jan. 2, 1951 FOREIGN PATENTS582,807 Germany Aug. 10, 1933

